Radio receiving circuits



Q\Q.\&k V n V. m A v N 1 Sept. 20, 1927.

Patented. Sept. 20, 1927.

. "UNITED "STATES ERNEST w. nousn, or miuvrrnoirnrr, ALABAMA.

1 RADIO RECEIVINGI' omcurrsr Application: filed'Aug'nst 27, 1925-. serial: No. sac-r3;

This invention relatesgenerally to apparatus. designed for the reception andamplification of electric currents of minute intensities, such as experienced in the; transmission andreception of wireless, telephonic and-telegraphic signals.

One object of the invention is to provide a receiver employing electron tube amplitiers wherein a single tuningcontrol is em,-

ployed .to place-the set in resonance with any desired signal frequency within, the operating range of the apparatus.

Another object of the invention is to provide a receiverandamplificr of the type set forth which will operate to equal advan' tage when connected to collectors or receiv-- ing antennas of any approved type, such as outsid'e aerials or indoor loops, and wherein a single tuning, control is provided, said control having substantially fixed and definite positions at-Which' the apparatus is in resonance with any desired signal frequency within the operating range of the apparatus, and. which positions, having been once ascertained, remain substantially unchanged regardless of the type of antenna to which the apparatus is connected. c

WVi-th these and other objects in view the invention consists in certain new and improved details of construction and combinationof. parts, one embodiment of which is fully described in the following specification and illustrated diagrammatically in the accompanying drawing. 7

Referring to: the: drawing more in detail the reference numeral 1 designates an in.- p-ut coil or couplerhavinga single winding of any suitable number of convolutions, the extremities of said coil being connected to the usual input binding posts-of the apparatus, such as indicated at 2 and 3, respectively The terminals of the coil 1 are also connected directly to thegfilarnent and grid input electrodes of the first radio frequency amplifying device 4, which is preferably an electron tube of the usual 3-electrode type having filament, plate and grid elec- The plate and filament output electrodes of thetube l'are connected to the terminals of the primary winding? of a radio frequency transformer T, the secondary winding S of which is connected to the input electrodes of a second electron tube 5, saidv tube serving as a combined detector and amplifier, and to this end the input circuit thereof is provided with the usual grid condenser 6'and' resistance element 7, said resistance element being made variable if be. of any approved type, but it is preferredv to construct these elements with a low-loss winding such as. of the open basket weave.

type, and the secondary winding of the transformer is preferably constructed so asto possess substantially the same electrical characteristics, asthe coupler coil l, it being noted that said coupler coil comprises a. single continuous winding.

The output electrodes of the tube 5: are connected to a telephone receiver 9,, or any other suitable reproducing device, said device being preferably shunted by a small fixed. condenser 10 whereby to side-track or bypass stray radio. frequency currents therefrom The usual sources of energizing potentials are provided for the filament and plate circuits of the tubes, these being; indicated at and B, respectively, it being noted that the plate circuit of the radio frequency amplifier 4 carries a considerably higher poatuning control in the antenna or input circuit of the receiver would render the operating character of the set exceedingly poor, and it is doubtful if the apparatus would function at all without the addition of a considerably more complex tuning control in the input circuit of the detector or elsewhere. It has been found, howevenfthat by suitably coupling the output circuits or electrodes of the radio frequency tube 4 and the detector'tube 5, not only does the single condenser 8 serve admirably to selectively determine and control the resonant frequency of the apparatus, but that such a coupling has also been found to increase the lib the apparatus connected as above described, it is apparent'that the absence of amplif ing power oi the set many times and to rcn er the apparatus more selective and its reproduction remarkably clear and free from the usual background of forei m noises so revalent in multistage ampl' ers.

'10 this end the plate electrode of the detector tube is coupled to the plate of the 'adio frequency amplifying tube through a by-pass circuit 11 containing a variable caaaclty such as indicated at 12, it havin been determined that a condenser so placer, while being instrumental in obtaining the advantages above noted, has substantially no effect upon-the resonant frequency of the apparatus, it serving merely to couple the out )ut circuits of the amplifier and detector, whi e variations in its capacity function only to regulate and controlthe amount of coupling or rate of transfer of encr" i from one output circuit to the other, thereby n1aking it possible to operate the tubes at a point as close as qossible to the point of: oscillation at whiclu as is well known, the tubes are most sensitive and ellicient.

As hereinbcfore indicated, the apparatus above described is designed to operate in connect-ion with antennas or collectors of any approved type, the terminals 2 and 3 serving as means of connection for the usual aerial and ground connections if an aerial-ground system is employed, whereas if an indoor loop is einj iloyed the same terminals are used to connect to the respective extremities of the coil, as shown in dotted lines in the diagram.

In operating the apparatus, assuming the terminals 2 and 3 have been connected to a suitable collecting system and the tubes -Il: and 5 energized through suitable sources of potential as shown at A and B, the tuning'eondcnser 8 operated in connection with the by-pass condenser 12, the former functioning to vary the resonant frequency of the apparatus, while the latter, by controlling the amount of coupling between the output electrodes of the amplifier and detector, functions to keep the tubes operating at their pointof greatest eiliciency, namely, that just below their respective points of oscillation.

\Vhile I have described and illustrated a preferred embodiment of my invention, it is to be understood that the output of the detector tube may be operatively associated with one or more stages of audio frequency amplification without departing from the s irit oi the invention, the description and i lustration comprising this application being for the purpose of example only and not as defining the limits of theinvention, which are to be determined from the scope of the appended claims.

Having thus described the invention what is claimed as new is:

1. In a signaling system, the combination of thermionic tubes having plate, grid and filament electrodes, and including an amplifier tube and a detector tube operatively associated with each other, and a direct cou pling between the plate electrodes of the amplifier tube and detector tube, said coupling including means for controlling the energy transfer between said plate elec trodes.

2, The combination described in claim 1, wherein the amplifier tube and the detector tube are inductively cou led together and variable condenser in sliunt with said inductive coupling between said coupling and the detector tube.

3. The combination described in claim 1, wherein the plate filament circuit of the amplifier tube is inductively coupled to the grid filament circuit of the detector tube, and wherein the control means included in the plate coupling between the tubes includes a variable condenser.

4. In a signaling system, the combination of thermionic tubes having plate, grid and filament electrodes and including a radio frequenc amplifier and a detector, the plate and t 1e filament electrodes of the radio frequency amplifier tube being connected by an inductance, the grid and filament electrodes of the detector tube being (ill connected by a second inductance, said two inductances being inductively coupled and arranged with their polarities reversed with respect to each other, and a direct coupling between the plate electrodes of the two tubes.

5. The combination described in claim 4 wherein the plate coupling includes a variable condenser for controlling the energy transfer between the plate electrodes.

(3. The combination described in claim 4, wherein the grid and filament electrodes of the amplifier tube are connected by an inductance, which inductance possesses substantially the same electrical characteristics as the inductance connecting the filament and grid electrodes of the detector tube and a variable condenser in shunt with the inductance in the detector grid-filament circuit.

ERNEST W. HOUSE. 

